Unwanted body hair, particularly dark hair on the face, legs, back and chest is a cosmetic concern for many people. Laser light has been used for cosmetic hair removal. To minimize damage to tissue surrounding hairs, some hair removal methods apply narrowly focused beams of light to a single hair or hair follicle. For example, U.S. Pat. No. 3,834,391 to Block discloses using a probe positioned at the top of a single hair duct to direct a narrow, focused beam of light down the hair duct beside the hair shaft, and thence to the papilla to coagulate papillar vessels. The Block patent also discloses that introducing mineral oil into the hair duct, for example, by rubbing it on the skin, helps transmit the light to the papilla. According to the Block patent, light energy is applied until the hair can be pulled out easily with tweezers. U.S. Pat. No. 4,388,924, to Weissman et al. discloses directing a narrow, focused beam of light in short duration, high intensity pulses to the epidermis adjacent a hair such that an extension of the beam intersects a single hair follicle at an angle through the skin.
Another approach, disclosed in U.S. Pat. No. 5,059,192, to Zajas, applies pulsed light having a wavelength of 694 nm, which wavelength is selected for absorption by melanosomes at the base of the hair follicle and papilla. The pulse duration is shorter than the thermal relaxation time of the melanin. The laser beam is directed from a position substantially vertically over a hair duct to the papilla.
U.S. Pat. Nos. 5,226,907 and 5,425,728, to Tankovich, the entire disclosures of which are herein incorporated by reference, disclose applying a light-absorbing contaminant topically to a skin section to be treated so that a portion of the contaminant enters hair follicles. The contaminant can be a water or oil-based suspension or solution containing chromophore particles having a high absorption at or near at least one frequency band of light. The chromophore particles, for example carbon or graphite particles, are generally sized too large to penetrate the barrier layer of the stratum corneum, but small enough to readily infiltrate the hair ducts to the hair follicles. Laser pulses are used to drive the contaminant down hair ducts and deep into hair follicles. The skin section containing the infiltrated hair follicles is then illuminated with a light beam that is highly absorbed by the contaminant, but that passes readily through skin. By this procedure, the hair cells surrounding the follicle that are responsible for hair growth are damaged or destroyed by energy transferred from the irradiated contaminant to the tissue surrounding the hair follicle.
Bleaching can make unwanted hair less noticeable. Chemical bleaching agents typically work only on the portion of the hair shaft above the skin surface. The unbleached portion below the skin surface rises above the skin and becomes visible as the hair continues to grow. U.S. Pat. No. 4,792,341, to Kozikowski et al., discloses using laser light to photobleach locks of hair that have been glued to transparent plates. Kozikowski et al. provide a table of optimal conditions for photobleaching using wavelengths of 530 nm and 1.06 .mu.m to destroy melanin in hairs that are removed from the body.
U.S. Pat. No. 5,423,803, to Tankovichi et al., the entire disclosure of which is included by reference herein, discloses a cosmetic method of skin resurfacing using laser light to give the skin a smoother appearance. A contaminant that absorbs light is applied to the skin so as to infiltrate the contaminant in gaps and crevices between surface layers of the stratum corneum, which is composed of about 20 layers of dead cells and which helps to provide a barrier to entry of harmful substances into the skin and thence the bloodstream. The skin surface bearing the contaminant is then illuminated so that the contaminant absorbs enough energy to exfoliate the outermost three or so layers of cells in the stratum corneum without significant damage to living cells below the stratum corneum.
Confocal microscopes are capable of providing images of sections of objects in nonscattering or weakly scattering media. A sample is scanned with light at a selected focal depth. The reflected image signal is passed through a small aperture positioned in front of a photodetector. The aperture cuts off portions of the image signal scattered from outside the focal plane. However, if an object is embedded in a highly scattering media, the signal to noise ratio of the image signal becomes vanishingly small very quickly as the focal plane is moved deeper into the scattering media. Schmitt, et al., in "Confocal Microscopy In Turbid Media," J. Opt. Soc. Am. A, Vol. 11, No. 8, pp. 2226-35 (August 1994), report that the scattering imposes fundamental limits on the sectioning capability of the microscope. Confocal microscopes cannot image objects more than about 200-300 .mu.m deep in tissue, such as skin.